Jupiter's Scar

Since spring, my telescope has ignored its job as a “go-to” — it has become a “no-go.” For those not in the know, a go-to telescope is a computerized gizmo which, properly set up, can point to anything in the heavens whose coordinates are known. Although I have tried to re-instruct it about aiming, something is wrong. I’ll do a reset the next time I’m out.

I thought I had worked through the problem last Wednesday when I drove to my favorite site in Emery County. Once set up, however, the telescope’s errors were evident as it pointed off wildly. Standing by my folding table under a lovely, spangled, moonless sky, I worked all night to resolve the problem. But it remained as obstinate as ever. Instead of finding galaxies I had never seen or spectacular dim nebulas, I was stuck with examining bright objects that were easily recognizable, to which I could steer the telescope without difficulty. One of these was the Pleiades, the fine star cluster.

Another was Jupiter. Like every other serious amateur astronomer, I’d heard about the discovery by Anthony Wesley, a resident of Murrumbateman, Australia. A few day before he had made a magnificent photograph of Jupiter, using a homemade 14-inch-diameter telescope. Close to the planet’s south pole (which he placed toward the photo’s top), was a black spot.

Familiar with Jupiter’s clouds, festoons and storm patches, Wesley knew he had found an impact scar. It was similar to the chain of scars that showed up when fragments of Comet Shoemaker-Levi 9 bombarded Jupiter’s atmosphere almost exactly 15 years before.

After Wesley announced his discovery, the Keck telescope in Hawaii made an infrared photo, and NASA used the newly-installed Wide Field Camera 3 of the Hubble Space Telescope to examine the spot. The images verified it was a collision mark and not some freak of Jupiter’s violent weather. Most likely the impactor was a comet. In following days the mark became elongated, as had happened with the 1994 splashes.

Scientists say the scar is as large as Earth, but that doesn’t make it easy to see. Compared with Jupiter, which could contain 1,000 Earths, our hometown is just a little burg. An Earth-size object 360 million miles away looks like a flyspeck. As the Sydney (Australia) Morning Herald noted, “To most people the image is unremarkable and appears as little more than a scar on Jupiter’s vast gas surface.”

The UtahAstronomy newsgroup discussed Wesley’s find, and I asked if it might simply be the shadow of one of Jupiter’s moons. No, said an amateur who knows more about it than I, it’s at the wrong latitude.

From my Emery County site, I observed Jupiter early Thursday morning. Patrick Wiggins, a NASA solar system ambassador to Utah, told me the spot should be visible that morning around the time Jupiter transits —- that is, reaches its highest in the sky, which happened to be when it was farthest south. I waited until it had cleared nearby trees and seemed southerly. When I looked through the scope, I thought I had detected the scar near the center of the planet, close to the Great Red Spot.

I was delighted to photograph the dark, round blotch. But later I learned I had been too eager to start the camera. The “scar” was only the shadow of the Jovian moon Callisto, which was providing a solar eclipse for any gassy creatures in its path. I had begun before transit and before the scar had rotated into view.

[On the right of my photos, with Jupiter’s south pole at the top, I can make out the moons Callisto and Io. The Great Red Spot, a storm that has been churning for at least 300 years, shows up in a “cove” of a dark southern cloud band to the upper left of Callisto’s shadow.]

I made telescopic photos of Jupiter from 2:03 a.m. until 2:24 a.m. (my camera makes note of the time). The scar actually wasn’t visible when I started. Another drawback is that — because I had gone galaxy-hunting — I had attached a camera to my telescope that was great for deep space objects but not so good for planets; I should have used my Lunar and Planetary Imager, which builds up much larger photos of planets.

But I lucked out. By the time of the last few pictures, the scar had just rotated into view. It is faint but (I know now) exactly where it should be. By chance, I photographed Jupiter, two moons, surface banding, the Great Red spot, Callisto’s shadow and the new impact scar.

[Enlarged view showing the scar, Great Red Spot and shadow, which I took the morning of July 23, 2009.]

[Explanation of features on the enlarged view.]

These are poor views, compared with the excellent photos that Wesley made. For a look at one of his images in which the Great Red Spot and the scar are in nearly the same positions as in my view, see THIS SITE.

I ended the session by taking astrophotos of the planet Venus, “the morning star and the evening star”. The sun was below the horizon, trees were silhouetted against its pastel pink-white glow, and Venus shone above the desert dawn.

[Photo I took of my gear while imaging Venus, Emery County, morning of July 23, 2009.]

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